Colloidal Soft Matter Physics

Colloidal soft matter is a class of materials that exhibit rich equilibrium and non-equilibrium 0thermodynamic properties, it self-assembles (spontaneously or driven externally) to form a large diversity of structures, and its constituents display an interesting and complex transport behavior. In this contribution, we review the essential aspects and the modern challenges of Colloidal SoftMatter Physics. Our main goal is to provide a balanced discussion of the various facets of this highly multidisciplinary field, including experiments, theoretical approximations and models for molecular simulations, so that readers with various backgrounds could get both the basics and a broader, more detailed physical picture of the field. To this end, we first put emphasis on the colloidal physics, which allows us to understand the main driving (molecular and thermodynamic) forces between colloids that give rise to a wide range of physical phenomena. We also draw attention to some particular problems and areas of opportunity in Colloidal Soft Matter Physics that represent promising perspectives for future investigations.

Acanthocyte Sedimentation Rate as a Diagnostic Biomarker for Neuroacanthocytosis Syndromes: Experimental Evidence and Physical Justification

(1) Background: Chorea-acanthocytosis and McLeod syndrome are the core diseases among the group of rare neurodegenerative disorders called neuroacanthocytosis syndromes (NASs). NAS patients have a variable number of irregularly spiky erythrocytes, so-called acanthocytes. Their detection is a crucial but error-prone parameter in the diagnosis of NASs, often leading to misdiagnoses. (2) Methods: We measured the standard Westergren erythrocyte sedimentation rate (ESR) of various blood samples from NAS patients and healthy controls. Furthermore, we manipulated the ESR by swapping the erythrocytes and plasma of different individuals, as well as replacing plasma with dextran. These measurements were complemented by clinical laboratory data and single-cell adhesion force measurements. Additionally, we followed theoretical modeling approaches. (3) Results: We show that the acanthocyte sedimentation rate (ASR) with a two-hour read-out is significantly prolonged in chorea-acanthocytosis and McLeod syndrome without overlap compared to the ESR of the controls. Mechanistically, through modern colloidal physics, we show that acanthocyte aggregation and plasma fibrinogen levels slow down the sedimentation. Moreover, the inverse of ASR correlates with the number of acanthocytes (R2=0.61, p=0.004). (4) Conclusions: The ASR/ESR is a clear, robust and easily obtainable diagnostic marker. Independently of NASs, we also regard this study as a hallmark of the physical view of erythrocyte sedimentation by describing anticoagulated blood in stasis as a percolating gel, allowing the application of colloidal physics theory.

Bloody jello: Colloidal physics states acanthocyte sedimentation rate as a diagnostic biomarker for neuroacanthocytosis

ABSTRACTChorea-acanthocytosis and McLeod syndrome are the core diseases among the group of rare neurodegenerative disorders called neuroacanthocytosis syndrome (NAS). NAS patients have irregularly spiky erythrocytes, so-called acanthocytes. Their detection is a crucial but error-prone parameter in the diagnosis of NAS, often leading to misdiagnosis. Based on the standard Westergren method, we show that the acanthocyte sedimentation rate (ASR) with a two-hour read-out is significantly prolonged in Chorea-acanthocytosis and McLeod syndrome without overlap compared to the erythrocyte sedimentation rate (ESR) of controls. Thus, the ASR/ESR is a clear, robust and easily obtained diagnostic marker. Mechanistically, through modern colloidal physics, we show that acanthocyte aggregation and plasma fibrinogen levels slow down the sedimentation. This study is also a hallmark of the physical view of the erythrocyte sedimentation by describing anticoagulated blood in stasis as a percolating gel, allowing the application of colloidal physics theory.

On charge percolation in slurry electrodes used in Vanadium Redox Flow Batteries

In vanadium redox flow battery systems porous carbon felts are commonly employed as electrodes inside the flow channel. Recently, slurry electrodes (or flow suspension electrodes) were introduced as a potentially viable electrode system. Such electrode systems are little understood so far. Mass, momentum and charge transfer phenomena co-occur, interactions with each other are nearly impossible to capture experimentally. We present a novel discrete model of the particulate phase combining theories from fluid dynamics, colloidal physics, and electrochemistry with a coupled CFD-DEM approach. The methodology allows to visualize local phenomena occurring during the charging of the battery and to compute the net current of the slurry electrode system. We demonstrate that an increasing particle volume fraction enables the formation of conducting networks in the flow electrode until a threshold is reached. Our study concludes, that the assumption of all particles participating in the charge transfer as assumed in pure CFD investigations is not necessarily valid.

Non-affine lattice dynamics of defective fcc crystals

The mechanical, thermal and vibrational properties of defective crystals are important in many different contexts, from metallurgy and solid-state physics to, more recently, soft matter and colloidal physics.

Application of Multiscale Process Zone Model to Simulate Fracture in Polycrystalline Solids

In this work, an early proposed atomistic-based multiscale process zone model is revised and employed to simulate crack propagation and spall fracture in polycrystalline solids. The multiscale process zone model is capable of describing heterogenous materials by incorporating the effect of inhomogeneities such as grain boundaries, slip lines and inclusions. A consistent depletion potential resulting from fundamental principles in colloidal physics is used to describe the cohesive laws for both the grain interfaces and process zones in bulk materials, which provides microstructure-based interface potentials in both normal and tangential directions with respect to finite element boundary separations in contrast to conventional cohesive methods. The polycrystalline microstructure are generated by using the Voronoi tessellations. Two different approaches of treating the process zone are proposed. The multiscale process zone model is implemented in a Lagrange framework based on the Galerkin weak form formulation. In addition, to eliminate the zero-energy modes and avoid shear locking in the interphase elements, a reduced integration technique is adopted in simulations. Numerical simulations on crack propagation in materials with various cohesive strengths have been carried out, and they can describe both inter-granular and trans-granular fractures. Finally, the spall-fracture of a specimen under high-impact load is captured using the proposed multiscale process zone model.